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format

ICO

ICO is the Windows icon container holding several sizes in one file.

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What is a ICO file?

A container that bundles multiple icon sizes and colour depths, used for Windows icons and website favicons.

Technical characteristics

Representation
binary
Lossy
No
Transparency
Yes

Compatibility

  • Windowsfull
  • macOSpartial
  • Linuxpartial

Browsers: Chrome, Firefox, Safari, Edge.

Advantages of ICO

  • Multiple resolutions in one file
  • Universal favicon support

Limitations to know about

  • Limited to icon-sized images in practice

When to use ICO

  • Favicons
  • Windows application icons

Best practices

  • Include 16, 32 and 48 pixel variants for crisp rendering everywhere

Convert ICO files

ICO scores

Deterministic scores calculated from the structured facts above. Identical facts always produce identical scores.

Overall score

58/100

  • Archiving score

    100
    • lossless storage preserves the original data for future migrations
    • it is actively maintained and current

    Confidence 38% · evidence coverage 56%

  • Longevity score

    91
    • it is actively maintained and current
    • lossless storage preserves the original data for future migrations
    • it does not satisfy: mainstream applications ship support for it

    Confidence 41% · evidence coverage 75%

  • Printing score

    78
    • it is lossless, so decoding returns the original pixels exactly
    • lossless data means no compression artefacts appear at print resolution
    • only a narrow set of applications handles it

    Confidence 37% · evidence coverage 88%

  • AI score

    67
    • lossless pixels avoid compression artefacts leaking into training data
    • large lossless payloads cost bandwidth and memory
    • only a narrow set of applications handles it

    Confidence 36% · evidence coverage 71%

  • Editing score

    65
    • it is lossless, so decoding returns the original pixels exactly
    • lossless data survives repeated open-edit-save cycles without degrading
    • only a narrow set of applications handles it

    Confidence 38% · evidence coverage 88%

  • Photography score

    64
    • it is lossless, so decoding returns the original pixels exactly
    • lossless data survives repeated open-edit-save cycles without degrading
    • it stores data losslessly, so files stay large
    • some devices ask the person to install something first

    Confidence 30% · evidence coverage 78%

  • Web score

    53
    • every major browser engine renders it natively
    • browsers render it natively, so no conversion step is needed at request time
    • it supports transparency
    • it stores data losslessly, so files stay large
    • large lossless payloads cost bandwidth and memory

    Confidence 44% · evidence coverage 92%

  • Compatibility score

    45
    • every major browser engine renders it natively
    • it does not satisfy: it converts into many other formats, which suits automated pipelines
    • some devices ask the person to install something first

    Confidence 60% · evidence coverage 100%

  • Streaming score

    20
    • every major browser engine renders it natively
    • it stores data losslessly, so files stay large
    • large lossless payloads cost bandwidth and memory

    Confidence 31% · evidence coverage 63%

  • Performance score

    0
    • large lossless payloads cost bandwidth and memory
    • it stores data losslessly, so files stay large

    Confidence 21% · evidence coverage 100%

What ICO is recommended for

Every conclusion below is derived from the structured facts on this page — nothing is written by hand.

  • Transparency100/100

    • Because it supports transparency.
    • Because it stores a full alpha channel, allowing soft edges and partial opacity.

  • Browser compatibility100/100

    • Because every major browser engine renders it natively.
    • Because at least one shipping browser renders it.

  • AI compatibility100/100

    • Because lossless pixels avoid compression artefacts leaking into training data.
    • Because wide library support means common data loaders can read it.

  • Long-term archiving100/100

    • Because lossless storage preserves the original data for future migrations.
    • Because it is a current, actively maintained format.
    • Because it does not satisfy: a newer format already supersedes it, which shortens its support horizon.

  • Future-proofing100/100

    • Because it is actively maintained and current.
    • Because nothing in the graph supersedes it yet.

  • Printing suitability71/100

    • Because lossless data means no compression artefacts appear at print resolution.

What ICO is not recommended for

  • Everyday consumer usage25/100

    • Because some devices ask the person to install something first.
    • Because it does not satisfy: small files are easy to email, message and upload.

  • Operating system compatibility33/100

    • Because at least one mainstream platform needs extra software.

  • Software compatibility33/100

    • Because only a narrow set of applications handles it.

Related to ICO

File extensions

Data quality

Every claim on this page is classified as a verified fact, a derived fact or an assumption.

Overall confidence
80%
Verification status
verified
Last reviewed
2026-08-03
Verified facts
1

1 classified claim backed by 1 source.

  • Convert Always editorial review — Convert Always

Sources and review status

Review status: verified · confidence 80%

Last reviewed 2026-08-03 (revision 1).

  • Convert Always editorial review — Convert Always